Inspire Spellpower( Races of Stone, p. 141)
You can use your bardic music to increase the power of your allies' spells.
Perform (any one) 8 ranks, bardic music,
You gain an additional bardic music ability called inspire spellpower. Inspire Spellpower (Su): As a standard action, you can use music or poetics to inspire the spellcasting of allied spellcasters, making their spells more powerful. To be affected, an ally must be able to hear you perform. The effect lasts for as long as the ally hears you sing and for 5 rounds thereafter. The affected allies' effective caster level is increased by 1. You cannot inspire spellpower in yourself. Inspire spellpower is a mind-affecting ability.
Inspire spellpower follows all the normal rules of the bardic music ability, including using one of the character's daily uses of the ability.